From: "Steven Rostedt (Google)" <rost...@goodmis.org>
Describe what ftrace_hash_move() does and add some more comments to some
other functions to make it easier to understand.
Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
---
kernel/trace/ftrace.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 021024164938..2d955f0c688f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -169,6 +169,7 @@ static inline void ftrace_ops_init(struct ftrace_ops *ops)
#endif
}
+/* Call this function for when a callback filters on set_ftrace_pid */
static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
@@ -1317,7 +1318,7 @@ static struct ftrace_hash *alloc_ftrace_hash(int
size_bits)
return hash;
}
-
+/* Used to save filters on functions for modules not loaded yet */
static int ftrace_add_mod(struct trace_array *tr,
const char *func, const char *module,
int enable)
@@ -1431,6 +1432,7 @@ static struct ftrace_hash *__move_hash(struct ftrace_hash
*src, int size)
return new_hash;
}
+/* Move the @src entries to a newly allocated hash */
static struct ftrace_hash *
__ftrace_hash_move(struct ftrace_hash *src)
{
@@ -1445,6 +1447,26 @@ __ftrace_hash_move(struct ftrace_hash *src)
return __move_hash(src, size);
}
+/**
+ * ftrace_hash_move - move a new hash to a filter and do updates
+ * @ops: The ops with the hash that @dst points to
+ * @enable: True if for the filter hash, false for the notrace hash
+ * @dst: Points to the @ops hash that should be updated
+ * @src: The hash to update @dst with
+ *
+ * This is called when an ftrace_ops hash is being updated and the
+ * the kernel needs to reflect this. Note, this only updates the kernel
+ * function callbacks if the @ops is enabled (not to be confused with
+ * @enable above). If the @ops is enabled, its hash determines what
+ * callbacks get called. This function gets called when the @ops hash
+ * is updated and it requires new callbacks.
+ *
+ * On success the elements of @src is moved to @dst, and @dst is updated
+ * properly, as well as the functions determined by the @ops hashes
+ * are now calling the @ops callback function.
+ *
+ * Regardless of return type, @src should be freed with free_ftrace_hash().
+ */
static int
ftrace_hash_move(struct ftrace_ops *ops, int enable,
struct ftrace_hash **dst, struct ftrace_hash *src)
--
2.43.0
